From Corrupted Cistern (using Lutz's screenshots since they're better than what I would have taken):
From Unknown:
Edit - A couple more I remembered:
Hexen: Veil of Darkness uses sector trees/tree-textured walls as the map layout in its forest map, as well as tree decorations and Hexen's destructible trees.
Lost Civilization MAP07 also does the "corridors of tree textures" thing.